String Palindrome Program

Question

I created a string palindrome program, but I am getting a Nullpointer exception.

Here is the code that I have written:

public class JavaApplication2 {

    /**
     * @param args the command line arguments
     */
    char c[]={'i','c','i','c','i'};
    String s = new String(c);
    String s1=null;
    int i,j;
    char c1[];
    public static void main(String[] args) {
        //TODO code application logichere

        JavaApplication2 ja=new JavaApplication2();
        ja.palindrome();
        ja.ans();
        boolean b1= ja.ans();
        System.out.println(b1);
    }

    public void palindrome()
    {
        for(i=s.length()-1,j=0;i>=0;i--)
        {
            c1[j]=s.charAt(i);
            j++;
        }
    }

    public boolean ans()
    {
        String s2= new String(c1);
        if(s2.equals(s))
        {
            return true;
        }
        else
            return false;

    }
}

I can't figure out how to deal with it and exactly why this error is occuring.

Answer 1

The Problem is that char c1[]; is not inizalized. Therefore this line give you a nullpointer:

String s2 = new String(c1);

Inizalized the variable:

char c1[] = {};

Now the NullPointer is gone, but thats not the final version, you need to fill it with your logic.